RAAFASA, a couple of the guys are newbies and streamed for radar towers, so they could only go the tower, but the others are either experienced locals (BK) or imports (not sure of the backgrounds, but they could have been trained for either).
I think at the end of the day its about bums on seats, and to train someone in the tower you only lose a rated controller off the roster for a week or so (classroom days/visit to visual Sim in ML), whilst the app/dep training involves a much longer run in the Sim, these lessons work best with 2 trainees, therefore two app or dep controllers off the roster at the same time, which they cannot afford. Short sighted - yep.
It will get worse before it gets better, as a few of the Traffic Managers are leaving by years end and that means getting guys off of the tools to train on the SYTM role - without them the whole show stops - no app or dep!!